Ask your OB, if in the US, about schnucks free prenatals program. With a doctors prescription you can get a years worth of free prenatals.
Prenatal are not at all the same. Some are sourced from synthetic ingredients and contain GMO'S and pesticides. What you want is a whole food sourced organic prenatal vitamin. Typically rainbow light prenatal are good for those who want an easy 1 a day whole food based vitamin. It will provide you and your developing baby with the essential nitrients. Personally I use garden of life prenatals. You need to take a DHA supplement as well for your babies brain and nervous system development. One good option is Nordic naturals prenatal DHA.
Most prenatals are the same. I just take the ones from Walmart and they are fine.